As @dw1305 mentioned, I've 9 x 50w floods above my 2000L, very similar to the ones you linked. They are aprox 70cm from the substrate.
They can be fantastic value for money, although I couple of things I wish I did different.
Firstly, colour temperature of mine are "cool white", I'd rather something warmer to look at these days (don't think plants care either way)
Secondly, I'd look for ones where there is a single powerful LED, rather than a matrix of smaller ones (such as in your link) IF you're considering it to be open top. The matrix of smaller LEDs spoils the "shimmer" effect you can get if when the light bounces off the waves and fills your room with a feeling of aquatic goodness!
Thanks for the info. That’s a big help indeed.
next is to find a solution to suspend them. I’m thinking steel box section but can’t find an attractive corner piece.
Oh and this is now for the 1200cm tank in the living room. The 60cm upstairs will be a much simpler affair. I should probably run two journals!